The present invention relates to a method for correcting protruding defects or white or black defects on a color filter, which occur during a process to manufacture a color filter for liquid crystal display apparatus.
Referring to FIG. 6, description will be given below on an example of a method for manufacturing a color filter. On a transparent substrate 2 such as a glass plate, a light-shielding layer BM comprising striped pattern with line width of 20 xcexcm, pitch of 80 xcexcm, and film thickness of about 0.5 xcexcm is formed by screen printing. Next, on the light-shielding layer, a red colorant sensitive material R is coated. Then, a photo mask is placed and light exposure is performed. Next, a green pattern layer and a blue pattern layer are formed by the same procedure. Both longitudinal sides of each color pattern layer are overlapped on the light-shielding layer BM for a length of about 10 xcexcm, and the film thickness is about 2 xcexcm. Next, with the purpose of achieving physico-chemical protection, and of evenly adjusting and flattening the surface, a photo-curing resin is coated on the color pattern layer, and a protective film layer OP is formed in film thickness of about 2-3 xcexcm. Further, a film of indium tin oxide (ITO) is formed on the protective layer by vacuum film forming method, and electrode pattern is fabricated by mask deposition method, etching method, etc., and a transparent electrode layer is formed to prepare a color filter.
In the process to manufacture the color filter as described above, foreign objects xe2x80x9caxe2x80x9d such as dust are intermingled in the coating process to cost color sensitive material as shown in FIG. 6. If these objects remain on the color pattern layers R, G or B or foreign objects such as dust are attached on the surface of the color pattern layer, protruding defects xe2x80x9cbxe2x80x9d may be formed on the portions corresponding to the foreign objects such as dust when the protective layer OF is formed on the color pattern layer. Also, when dust is attached on the photomask, white defects xe2x80x9ccxe2x80x9d may occur on the color pattern layer or black defects may be generated on the light-shielding layer EM. Such defects may impair orientation of liquid crystals in liquid crystal cells, which are provided on the surface of the color filter, or may lead to defects in the images taken or displayed, and the products produced using the color filter may become defective. In the past, as described in JP-A-3-274504 or JP-A-9-184910, methods have been proposed to coat a colorant sensitive material after cutting the defective portion off and to remove it using the laser beam in order to correct the above defects.
However, according to the conventional method for correcting defects as described above, it is difficult to fill ink to corners when the corrective ink is dropped to the upper surface because about the entire region of picture element is cut in rectangular shape, and void patches or unevenly colored portions are likely to occur. Also, the quantity of the colorant to be removed is higher than the case when only the portion near the defects are cut off. As a result, colorant materials are splashed to the surrounding regions, and these may cause new defects. Further, in case the hue of the corrective ink is different by approximately one picture element from the hue of colorant picture element, defects are very likely to occur due to color difference. As a result, the percentage of acceptable products after correction may be low.
To solve the above problems, it is an object of the present invention to provide a method for correcting defects on a color filter, by which it is possible to correct all of protruding defects, white defects and black defects, which are generated in the process to manufacture color filter and to extensively improve the percentage of high quality products.
To attain the above object, an aspect of the invention provides a method for correcting defects on a color filter, which comprises the steps of setting a diameter of a laser beam in a circular correcting region including defective portion, or more preferably, in a circular correcting region comprising a circle which circumscribes the defective portion in order to ensure better permeation of liquid and better diffusion, and to prevent uneven coloring due to insufficient flow of the liquid when the defective portion on then color filter is removed by irradiation of the laser beam, dropping a corrective ink to upper surface of the circular correcting region by an ink jet unit so that the ink is formed in spherical shape after the circular correcting region has been removed, and hardening and shrinking the corrective ink by an ink hardener thereafter so that variation of film thickness in the circular correcting region can be controlled within 0.1 xcexcm.
The invention according to another aspect provides a method for correcting defects on a color filter, said method comprising the step of setting a diameter of a laser beam on a circular correcting region including defective portion when the defective portion on the color filter is removed by irradiation of the laser beam, and depositing a metal film of more than 1000 angstrom in thickness by laser CVD method on the circular correcting region after the circular correcting region has been removed so that back light can be completely shielded.
According to the present invention, it is possible to easily correct all of protruding defects, white defects and black defects caused in the process for manufacturing the color filter, and also to extensively improve the percentage of high quality products. Further, according to an aspect of the invention, ink can be dropped by selecting ink color depending on the defective region by the ink jet unit. For example, in case the correcting region is a green pattern layer, a green corrective ink can be dropped. As a result, defects on the green pattern portion can be easily corrected without resulting in uneven coloring.